Method and apparatus for optimalizing the operation of a system



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July 17, 1962 A. KERSTUKOS ETAL 3,044,701

METHOD AND APPARATUS FOR OPTIMALIZING THE OPERATION OF A SYSTEM Filed April 24, 1958 14 Sheets-Sheet 8 XmYm 2 Start wmuessss: Fig. 3 INVENTORS Albert Kerstukos Robert Hooke @wfl-NQ,

R ff and Richard c. Bollinger.

United States Patent 6 tric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Apr. 24, 1958, Ser. No. 730,590 25 Claims. (Cl. 235-151) This invention relates to the automation art and has particular relationship to the control of the components used in an industrial system or of the environmental conditions, such as temperature and pressure under which the system is operating. Such components and conditions are called herein the parameters affecting the system.

The invention concerns itself with any industrial system, the operation of which is dependent on a plurality of variable parameters. For example, the invention may be applied to the production of mono-styrene from ethylbenzene by mixing steam with the ethyl benzene and maintaining the temperature at a predetermined point. In this case, the variable parameters are the flow rate of the ethyl-benzene, the flow rate of the steam and the temperature. The quality of the product derived from this process is determined by measuring the refractive index of the resultingmono-styrene, which is a liquid. This index may be measured electrically, that is, an electrical magnitude, a potential for example, proportional to the index may be derived. While there are many other industrial systems to which this invention is applicable, the above example is typical, and in the following discussion this example will be referred to. It is not intended that such reference should in any way limit the scope of this invention.

It is broadly an object of this invention to provide methods and apparatus for changing automatically the variable parameters atfecting an industrial system in such a way that the operation of the system is optimalized and is maintained in its optimal condition.

It is another object of this invention to provide a method for setting automatically certain or all of the variable parameters affecting the operation of a system at settings such that the operation is at an optimum, and it is a further object of this invention to provide apparatus particularly suitable for practicing this method.

It is a further object of this invention to provide a method for optimalizing the operation of an industrial system by varying the critical variable parameters on which the operation is dependent, and it is still another object of this invention to provide apparatus particularly suitable for practicing this method.

Another object of this invention is to provide a method for continuously evaluating the operation of an industrial system as the critical variable parameters affecting the operation of a system are varied, and it is a further object of this inventionto provide apparatus particularly suitable for practicing this method.

A specific object of this invention is to provide a novel method of recording a magnitude measuring the operation of a system as the parameters which aiiect the operation are varied so that effective evaluation may be carried out, and it is another specific object of this invention to provide apparatus particularly suitable for practicing this method.

An incidental object of this invention is to provide novel memory recording or registering apparatus.

Another incidental object of this invention is to provide novel apparatus for evaluating the operation of a system.

An ancillary object oi this invention is to provide novel apparatus for measuring out increments of different length.

3,044,701 Patented July 17, 1962 A still further ancillary object of this invention is to provide for apparatus in which the operation of a system is controlled by changing variable parameters in accordance with a predetermined pattern, memory apparatus for identifying the point in the pattern at which the apparatus is operating at any time.

In accordance with this invention the operation of an industrial system is optimalized by varying critical or selected parameters of the system in increments in accordance with a predetermined pattern, comparing the operation of the system after each setting of the parameters with the highest operation obtained during prior settings and adjusting the polarity or the magnitude (or both) of the succeeding parameters in accordance with the results of the comparison.

The application of the invention may be understood by considering the above-mentioned system for producing styrene. Let the temperature be identified by the variable X, the flow rate of the ethyl-benzene by the variable Y and the flow rate of the steam by the variable Z. The increments of each of these variables which are added are identified as AX, AY, AZ. It may be assumed that initially the system is set at a point at which the variables have values X Y Z and that values of the parameters at optimum operation are X Y Z In accordance with this invention, the operation of the system is optimalized by adding combinations of the increments AX, AY, AZ, 'in accordance with the predetermined pattern which is repeated and evalcuating the operation after each setting until the setting X Y Z is achieved. Following each evaluation the magnitude and/ or the polarity of the new increments may be varied in accordance with the results of the evaluation. The addition of an increment to one or more of the parameters sets the system at a new point of operation. As the increments are added, the point of operation of the system is progressively moved from the initial point X Y 2,, to the point of optimum operation X Y Z in .a series of steps. The pattern which may be followed in the practice of this invention may take any convenient form. A typical pattern would be one including the following steps:

First step, the addition of all three increments, AX, AY,

Second step, the addition of only AX;

Third step, the addition of all increments AX,AY, AZ; Fourth step, the addition of only AY;

Fifth step, the addition of AX, AY, AZ;

Sixth step, the addition of only AZ. 7

With the system set at X Y Z the operation is measured and recorded and then the first increments are added. The first step would change the setting of the system to X -l-AX, Y -l-AY, and Z +AZ. The operation of the system at this new point is recorded and a comparison is made between the value at the initial point and the value at the new point. If the value at the new point is lower than the value at the initial point, the system is reverted to the initial point and the polarities of all or certain of the variables are changed. It may be assumed that the polarities of all the increments are changed. With the polarities of the increments changed the second step is carried out and thesystem is reset to a new point X -AX, Y Z The operation of the system is now again recorded and a comparison made. If in the case again there has been no improvement in the operation, the system is again reverted to its initial point and the polarity of the increment AX again changed. The third step is then carried out. This process is repeated until the system is set at a new point at which an improvement in the operation is measured. When an improvement is measured, the succeeding increment is added to the variable at the point at which the improvement is measured 3 and new comparisons are made with the recorded operation at this new point.

For example, if an improvement is measured following the second of the above-described changes, the third step is carried out from the point X,AX, Y 2,. The third step changes the system to the point X 2AX, Y -AY, Z,AZ. At this new point there is again a recording of the operation of the system and a comparison with the operation at the last point. This mode of operation continues until the operation of the system is optimalized at X01 Y! ZOI It may be that as the operation of the system in ac cordance with this invention is progressing, a region of optimum operation is passed. The evaluation of the operation may show improvements for a series of settings followed by a setting at which no improvement is shown. This would indicate that the system has passed through or around an optimum. This invention provides for such an occurrence. In accordance with this aspect of the invention the optimum point is now found or approached by adding increments which are substantially smaller than the increments originally added. The attainment of an optimum point is in the practice of this invention signalled by a predetermined number of successive incremental changes, none of which measure improvement. In the practice of this invention following this number of changes the system is set to detect any drift from maximum.

This invention includes within its scope, not only methods for optimalizing the operation of a system, but also apparatus used in the practice of the methods. For recording the operation of the system, a plurality of registers are provided in accordance with this invention. In one register the operation following each change is recorded. In another, the prior optimum operation is recorded. A third register serves for transferring the recordings so that the optimum operation is available in the second register for comparisons with succeeding operations.

In the practice of this invention the record in the first register is removed if the comparison reveals that the operation in the second register exceeds that in the first. If the comparison reveals that operation in the first register exceeds that in the second, the record in the first register is transferred to the second. This is accomplished efiectively by transferring the record in the first register to the third removing the record from the second register and transferring the record from the third register to the second.

In accordance with this invention, high precision in the recording of the operation of the system is achieved by recording the operation at each setting of parameters as a binary number defined by a plurality of off-on devices, such as relays or properly connected discharge devices, transistors, or magnetic amplifiers. For this pur pose the actuated condition of relay or the conducting condition of discharge device or transistor may be regarded as representing the number 1 and the unactuated or nonconducting condition as the number 0. The number of components used to define the operation may be selected to correspond to the desired precision, for example, seven components permit the counting of a number reaching the magnitude 127. This would permit recording of operation, for example, as measured by index of refraction, from 0 to 127; the three digits having any convenient denomination, such as 127, .0127, or .000127.

The records on the registers are evaluated by electrical circuits responsive to the conditions of the various relays or the state of conductivity of transistors or discharge devices. In accordance with a specific aspect of this invention, a novel evaluation apparatus for comparing registers of the relay type is provided. In this apparatus the contacts of the relays are so connected as to respond in one way if the number defined by one set of relays is higher than that defined by the other, and in another way if the converse is true.

The incremental changes in the parameters are in the practice of this invention effected electrically. In applying this invention to the making of mono-styrene, as disclosed above, the flow of ethyl-benzene and steam is controlled by valves, the openings of which may be controlled by electromagnets. The temperature may be controlled by electrical heaters. The parameters are then controlled by controlling the exciting currents of the electromagnets and the heating currents. The controls are effected by varying the potentials derivable from potentiometers or voltage dividers the settings of'which are determined by stepping switches or counters. In accordance with a still further specific aspect of this invention, a novel Counter Unit is provided for setting the potentiometers and thus measuring out the increments of the parameters to be added. This Counter Unit includes a Major Counter and a Minor Counter so interconnected that the Minor Counter counts the increments to be measured out by the Major Counter and interrupts the operation of the Major Counter once the predetermined number of increments are counted out.

It is one of the features of this invention that the addition of increments to the parameters follows a predetermined pattern. In accordance with one of the specific aspects of this invention, apparatus is provided which operates to identify the point in the pattern at which the optimalizing apparatus is operating.

Definition of Terms In describing the invention, it is convenient to use certain terms or expressions having peculiar significance with respect to the invention. It is believed desirable to define the principal terms or expressions which will be used.

A move is defined as the process of adding an increment such as AX, or AY, or AZ, or increments, such as AX, AY, AZ to a parameter or parameters.

A success is defined as a move which has resulted in the improvement of the operation of the system controlled.

A failure is defined as a move which has resulted in no improvement in the operation of the system. A failure may arise either where the operation of the system is the same as before the move or where the operation of the system is lower than before the move.

A modulo is defined as a step in the pattern of increments which are added to the parameter or parameters. Thus, AX, AY, AZ is the first modulo, AX the second, AX, AY, AZ, the third, AY the fourth, etc.

A register is defined as a system of relays by the actuation or unactuation of which a magnitude measuring the operation of the system is recorded as a binary number.

In the practice of this invention, the polarity changes and the magnitudes of the increments change as the optimalizing of a system progresses. Corresponding to these changes, the increments are regarded as having stati: a zero status, a first status, and a second status, and the apparatus is regarded as having two statesa first state and a second state. The increments are in status zero at the start of an operation and pass into status one after several moves, the number of moves preferably being different for each of the parameters. The increments pass into status one from status two after a success in state two. The apparatus is in state one at the start of an operation and passes into state two either when four failures occur at the start of an operation or when the parameters are all in status two. In state two the increments are smaller than in state one.

The novel features considered characteristic of this invention are disclosed generally above. The invention itself, both as to its organization and as to its method of operation, together with additional objects and advantages thereof, will be understood from the following description of a specific embodiment of the invention taken in connection with the accompanying drawings, in which:

FIGURE 1 is a block diagram showing the essential components of a preferred embodiment of this invention, and the relationship between these components;

acne r01 FIGS. 2A through 2F together constitute a circuit diagram of the preferred embodiment of this invention;

FIG. 3 is a graph illustrating the operation of this invention; and

FIGS. 4A through 4F constitute stem sheets showing the stem and contact arrangements of the relays of FIGS. 2A through 2F.

Introductory Explanation The specific embodiment of the invention disclosed herein is apparatus for setting two variables X and Y of a Controlled System so that the operation of the system is at an optimum. With reference to the example discussed above, the two variables may be any two of the three mentioned, that is, the flow of ethyl-benzene and the fiow of steam or either of these and the temperature. A twovariable control is selected for the purpose of facilitating the explanation of the apparatus. The variables are X and Y and the pattern of increments which is followed by the apparatus disclosed herein includes the steps AX and AY; AX; AX and AY; AY. This invention, in its broader aspects, is applicable to the control of three or more vari able parameters.

The specific apparatus disclosed includes a plurality of relays, each having a plurality of contacts. Each relay is identified by capital letters or capital letters and numbers which have a general significance as to the purpose of the relay. Thus, a relay may be identified by letter A or by A1. The contacts of the relays are identified by lower case letters which appear after the capital letters. For example, a contact of relay A1 is identified Ala or Alb. In the discussion the contacts of the relays are referred to simply as front and back rather than as front contact and back contact. A front is a contact which is open when the relay is deenergized and a back is a contact which is closed when the relay is deenergized. In the drawings, the relays are represented by rectangles. Relays which drop out a predetermined time interval after they are deenergized are represented by rectangles, the long sides of which are double lines. There are also time delay relays in which the delay is produced by a capacitor connected to discharge through the core after the supply to the coil is interrupted. Front and back contacts are represented by their conventional symbols. To facilitate the understanding of this invention, the conditions of the relays and the contacts during the stand-by condition of the apparatus are indicated. A relay which is actuated during stand-by is identified by a dot near or in the symbol. A contact of an energized relay is identified by a dot near the symbol. Thus, a dot adjacent to a symbol for a back contact means that during stand-by the contact is open.

The general functions of the various relays included in the apparatus disclosed herein are given briefly in the following table:

Relay Function Starting relay. Actuation of this relay starts optimalizing operation which then proceeds automatically to reset.

Status relays actuated when the parameters X and Y are in status 0. Corresponding relays for status 1. Corresponding relays for status 2. Change-of-status relays for afieeting change from status 1 to status 2. Auxiliary relays involved in change-of-status.

Positive polarity relays actuated when X or Y increments have a positive polarity.

Negative polarity relays.

Change of polarity relays actuated on the occurrence of a failure to produce a change of polarity in the corresponding increment. Auxiliary relays involved in change of polarity.

This relay is actuated to set the apparatus in state 2.

Modulo relays. Actuated when apparatus is in a modulo corresponding to the relay.

PX, PY

PXl, PYl, QXl, QYl, PC

STZ

M1, M2, M3, M4

Relay Function M, M11, M21, M31, M41

NlB, LIB

A1 through A7 Bl through B7 01 through 07 AS, BS, OS, A, B, O

EA, EB, no

CA l

- RV, NT, DM

HA, KA, HS, KS

NA, NS, MA, MS, NH, KT, KL.

LIB, LIB, NIB, N4B

NR, LR HA, HS, KA, KS

Auxiliary relays actuated during the change from one modulo to the next. Actuated to start the measuring out of the increments. Actuated to stop the measuring out; when a long increment has been measured out. Actuated to stop measuring out when a short increment has been measured out. Relays of A Register which carries the highest magnitude of operation for a series of prior moves. Relays of B Register which carries the magnitude of the operation for each new move. Relays of 0 Register for transferring highest magnitudes between B and A. Auxiliary relays associated with Registers A, B, and C, respectively. Relays A, B, and C are actuated when Registers A, B and C carry a record. Actuated to reset A, B, or O Registers. Actuation initiates transfer of record from B Register to C Register in the event of a success. Actuated to transfer record from 0 Register to A Register. Actuate to cause record of operation to be transferred to A Register at start of an optimalizing process. Actuated a predetermined time interval after increments are added to permit transfer of magnitude of operation of controlled system to Register B. Actuated to cause recording of system operation in Register B in dependence on setting of D conac s.

Actuates DB alter increment has 1 been added to system. Auxiliary relays controlling RD in response to DA and DB. Maintains change of modulo in case of delay in operation of change of polarity or change of status relays. Actuated to start evaluation of record in B Register, that is, comparison with record in A Register. Auxiliary relays introduce time delay between recording in B Register and evaluation. Actuated when a failure occurs. Actuated when a success occurs. Betermmes operation of optimalizmg apparatus selectively in response to success or failure. Cooperate to return Controlled System to setting before move on occurrence of failure. Major counters for measuring increments in parameters. HA counts X increments in a forward direction; KA counts Y increments in a forward direction; HS and KS count in a reverse direction. Prevents major counters from re setting to 0 when the wipers have completed a cycle (contacts of ma or counters are arranged in complete circles). Minor counters. Cooperate with HA, S, KA, KS, to measure increments. Determine magnitudes of increments. L413, NAB produce four times magnitude of LIB, N113. Reset coils for N and L. Auxiliary relays producing eooperation between HA, HS, KA', KS and N and L, respectively. Minor counter for counting successes in state 2. Auxiliary relay for interlocking Ci-GR so as to prevent malfunchoning. Auxiliary relay cooperates with G-GR to produce counting. Failure counter, counts both in state 1 and state 2. Afuliriliary relay causes counting 0 1 ure. Set A and B Registers to record drift.

Drift relayStarts a new optimalizing operation following success after eighth failure.

Description In the block diagram shown in FIG. 1, the system which is to be optimalized is labeled Controlled System. The increments AX and AY are added to the parameters X and Y of the Controlled System by a controller which is electrically controlled from the Major Counter Unit through a. pair of potentiometers POTX and POTY (FIG. 2F) respectively. A quantity proportional to the operation of the Controlled System is derived from the controlled system through an Output Converter.

The apparatus in accordance with this invention includes additionally to the Major Counter Unit, a Minor Counter Unit, the counters of which are so interconnected with the counters of the Major Unit as to count out increments of the proper magnitude. The apparatus also includes a Counter Control Unit which causes operation of the Counter Unit under the proper circumstances.

The apparatus includes a Starting Unit for starting an optimalizing operation. The Starting Unit is actuable by instantaneous closing of a push-button SW and the optimalizing operation continues automatically once this button is released and permitted to reopen. The Starting Unit is connected to the Output Converter and when actuated conditions the Output Converter to transmit a magnitude proportional to the operation of the Controlled System.

The apparatus further includes Registers A, B and C in which are recorded the magnitudes involved in the operation of the System as binary numbers. Registers A and B are adapted to be connected to the Output Converter through a plurality of selectively operable contacts D (FIG. 2C) corresponding in number to the relays of the Registers. These contacts D are set by the Output Converter to define as a binary number the magnitude of the operation of the Controlled System at any time. At the start of the operation, the initial setting of the Controlled System is recorded in Register A following actuation of the Starting Unit. The apparatus includes a Status Polarity Unit and Modulo Unit which are interconnected with Register A so that once the magnitude is recorded in Register A, the Modulo Unit is set to correspond to the first move modulo (AX and AY) of the pattern. The Modulo Unit is interconnected with the Counter Control Unit and the Major Counter Unit so that on being set, the Modulo Unit causes the Major Counter Unit to be actuated to introduce the first move into the controlled system.

The apparatus also includes a B-Register Setting Unit. This Unit is interconnected with the Major and Minor Counter Units and with Register B so that once the first move is completed, a magnitude corresponding to the operation of the Controlled System at the new setting is recorded in Register B. The connection is through a timer (relay RD, FIGS. 2C and 2E) which times out only after a sufficient interval elapses to enable the Controlled System to stabilize so that the magnitude of its operation is reasonably approximate to the final magnitude of operation which would be attained in the new setting. If the trend of the operation of the Controlled System is non-oscillatory towards an increase or a decrease, it is not necessary that the system reach its final operation following the first or any later move before the operation is recorded in Register B. It is only necessary that the record in Register B clearly show whether an increase or a decrease has occurred. Where the System is non-oscillatory, this will be manifested after a relatively short time interval.

Once the recording in Register B is completed, the magnitude in Register A and the magnitude in Register B are compared by an Evaluate Unit which is actuated when the record in Register B is complete. The Evaluate Unit has two responses, one for the case in which the record in Register B is higher than the record in Register A, and the other when the records are equal or when E is lower than A. When the record in Register B is higher 8 than in Register A, the move is a success. Otherwise, the move is a failure.

The apparatus includes a B-C Register Transfer Unit which is actuable by the Evaluate Unit in the case of a success. This Unit causes the record in Register R to be transferred to Register C. The record in Register A is then removed and the record in Register C is transferred to Register A by a C-A Register Transfer Unit. The new record represents operation of a higher magnitude of the Controlled System than the record removed. When the record in Register A is removed, the Modulo Unit is actuated and sets to a new modulo in the pattern. Once the transfer from Register C to Register A is effected, the record in Register C is removed. With this removal, a successful move is completed. The Major Counter Control Unit is then again actuated to introduce another increment into the parameters of the Controlled System.

In the event of a failure the Evaluate Unit operates through the Register Release Unit to remove the record from Register B and then through the Return Unit to return the Major Counter Unit and POTX and POTY to their settings before the move. In addition, the Status Polarity Unit is actuated to change polarity or status and the State Unit is actuated under certain circumstances to change state. The apparatus also includes a Return Unit. The Return Unit is actuated by the Evaluate Unit in the event of a failure and actuates the Major Counter Unit to return the Controlled System to the setting which this System had prior to a move which failed.

The apparatus further includes a Success Counter Unit and a Failure Counter Unit. The Success Counter Unit operates only with the apparatus in state 2, and resets the apparatus to state 1 and the increments to a lower status than 2 on the occurrence of a predetermined number of successes. The Failure Counter Unit operates to count failures and to control the state and the operation of the apparatus at and near the optimum point of the systern.

In FIGS. 2A through 2F, the optimalizing apparatus is shown in detail. The apparatus is supplied from conductors LP and LN of a direct-current supply of adequate potential to actuate the various relays.

The Starting Unit includes relays ST (FIG. 2D), DA, R, RC and RD (FIG. 2C). The coil of ST is adapted to be connected between conductors LP and LN through the pushbutton SW and to be locked in through its front SP1: and back Ak. During drift the coil of ST may also be connected between conductors LP and LN through the front DRFb.

The coil of DA is adapted to be connected between LP and LN through front STc, back An, back Ba. The coil of DA is adapted to be locked in through back Ab and front DAb. The coil of DA is also adapted to be connected between LP and LN through front FCd, front FCTa and back UFp. This sets the apparatus for drift.

The coil of R is adapted to be connected between LP and LN through front DAd or through front DBd. DAd is closed at the start and DBd during subsequent moves. The coil of RC is adapted to be connected between LP and LN through back Ra, and the coil of RD is adapted to be connected between LP and LN through front RCa. To produce the desired timing in the operation of RD, the coil of RD is shunted by capacitors and resistors, certain of which may be shunted out by back F8Bg. F8Bg is opened during drift. RD has a back RDa which controls the Output Converter (FIGS. 1 and 2E) conditioning it to operate. With F813 actuated, the delay between the actuation of DB, that is, the completion of insertion of the increment in the Controlled System, and the dropping out of RD which permits the transmission of a magnitude corresponding to the operation of the Controlled System to the Registers is greater than with FEB unactuated. The significance of this is that during drift after the System has locked in through X110.

reached an optimum the delay between the repeated checks of the System to determine if the System has drifted from maximum is substantially greater than the duration between moves when the System is being set to its optimum by incremental changes in the parameters.

The Status Polarity Unit (FIGS. 2A, 2B) includes the status relays X0, Y0, X1, Y1, and X2, Y2, the changeof-status relays CSX and CSY, the polarity relays PX and FY and QX and QY, and the change-of-polarity relays XP and YF. In addition, there are auxiliary relays X11, X21, Y11, Y21, CCX, CCY, PXI, PY1, QX1, QY1, and PC. The coil of X is adapted to be connected between LP and LN through front STe, and to be locked in through front Xtla and back M301. The coil of Y0 is adapted to be connected between LP and LN through front ST and to be locked in through front X0h and front Y0a or through back Mla and front Ytlzz. The coils of X1, Y1, X2, Y2 are connected in parallel through back STd to LN. The coil of X1 is connected to LP through back X02, and back X2e. The coil of Y1 is similarly connected to LP through back Y03 and back Y2e. The coil of X2 is adapted to be connected to LP either through front GRRc or through back 631% and through front X11a and back CSXd and to be locked in through front X2 and back X21c or front CSXe. The coil of Y2 is similarly adapted to be connected to LP through front GRRc or back G3Bb, and front Ylc and back CSYc or front Y2) and back Y21c or front CSYb. The coil of X11 is adapted to be connected between LP and LN through front CSXc and front Xle and to be The coil ofY11 is analogously adapted to be connected. The coil of X21 is adapted to be connected between LP and LN through front X2j and back CSX and to be locked in through front X21d. The coil of Y21 is analogously adapted to be connected. The

coil of CCX is adapted to be connected between LP and LN through front X2 and back CSX and to be locked in through front X21d. The coil of Y21 is analogously adapted to be connected. The coil of CCX is adapted to be connected between LP and LN through front X2 and front X21a or front Xla and front Xlla. The coil of CCY is analogously adapted to be connected. The coil of CSX is adapted to be connected between conductor LP and LN through the following alternative paths:

In state 1, front M2h, front X10, front CMr, front UFn; In state 1, status 2, front M3d, front X2d, back STZg,

front CMr, front UFn;

In state 1, status 2, through front Mli, front X2d, back STZg, front CMr, front UFn.

In status 2, front M21, front X2c, front USO;

In status 2, state 2, front M1h or front M3h, front Y2d,

front STZp, front X2c and front USO.

Back STZg is shunted by front Xld. The coil of CSY is analogously adapted to be connected.

The coil of PX is adapted to be connected between LP and LN through front STm, or through back XF and front QXlb. The coil of PX is adapted to be locked in through front PXa, and back QXa. The coil of FY is analogously adapted to be connected. The coil of PX1 is adapted to be connected between LP and LN through front PXc, front XFd, and to be locked in through front PXla. The coil of PYI is analogously adapted to be connected. The coil of QX is adapted to be connected between conductors LP and LN through back XFc and front PXlb and to be locked in through front QX and back PXb. The coil of QY is analogously adapted to be connected. The coil of QXI is adapted to be connected between LP and LN through front XFe and front QXc and to be locked in through QXla. The coil of QY1 is analogously connected. The coil of XF is adapted to be connected between conductors LP and LN through back Y1 front MMln, front X6), front CMw and front UFt. Y1 is shunted by front X0g, M1n is shunted by M3m, X0) is shunted by front X2k. Y1 and Mln are shunted by M21.

It is seen that XF is not actuable in status 1. This means that in the event of a failure in status 1, a change of polarity does not occur.

YF is connected between conductors LP and LN similarly to XF and in this case also the connection is such that a change of polarity does not occur on failure in status 1. The coil of PC is adapted to be connected between LP and LN through XFb in the following alternative circuits:

Front X0z', front PXlc Front X21, front QXlc Front Xtli, front QXlc Front X21, front PXlc Front Yttf, front PYle Front Y2 front QYle Front YtlFf, front QYle Front Y2j, front PYle The State Unit includes the relay ST2 (FIG. 2A). The coil of this relay is adapted to be connected between conductors LP and LN through STo, and front FFb; or through back STo and front X2i and Y2h. The coil of ST2 is adapted to be locked in between conductors LP and LN through front ST2t, and back G3Ba. Operation of FF thus transfers the apparatus from state 1 to state 2. In addition, the apparatus is transferred to state 2 when both X2 and Y2 are in status 2. Operation of G3B which results from three operations of G while the apparatus is in state 2, reverts the apparatus from state 2 to state 1.

The Modulo Unit (FIG. 2B) includes relays M1, M2, M3 and M4 and transfer relays M, M11, M21, M31 and M41. The transfer relays M11, M21, M31, M41 are of the type which pull in immediately when their coils have been energized but drop out after a short delay after the current through the coils is interrupted- The coils of M1, M2, M3 and M4 are connected to conductor LN through back STi. Thus when ST'is actuated, the coils M1, M2, M3 and M4 are deenergized. The coil of M1 is adapted to be connected to conductor LP through the following alternative circuits:

Front Ma, front Mb, front Xtlb, back M2a, front Ytlb Front Ma, front M41d, back M20 Front Mlb, back M20 The last is a lock-in circuit. The coil of M2 is adapted to be connected to conductor LP through front Ma, front M111), back MSc, and to be locked in through front MZe. The coil of M3 is adapted to be connected to LP through front Ma, front M21b, back M40 and to be locked in through front M3a. The coil of M4 is adapted to be connected to LP through front Ma, front M3111, back Mlc, and to be locked in through front M411. The coil of M11 is adapted to be connected between conductors LP and LN through front CMe, back Me, front Mld, and to ,be locked in through front Mlla. The coils of M21, M31 and M41 are analogously connected. The coil of M is adapted to be connected between conductors LP and LN through back CMb and through the following parallel networks:

Front Ad, front Xtta, front Y0a Front NCa Back STg, front Mi Front US) Front UFg, front XFg or front YFf, front PC Front UFg, front CSXb, front CCX) Front UFg, front CSYg, front CCYa this mode of labeling in mind, the state of the various relays involving contacts of relays M1 through M4, that is, whether they are energized or deenergized, in different modulo can readily be determined.

The Counter Control Unit (FIG. 2B) includes the relay T. The relay T is connected between conductors LP and LN through back CMa, front Me, back FSBa, and back PO: and the following parallel circuits:

Front M410, front Mll, back M41 Front M310, front M411, back M3k Front M2d, front M3l, back M2k Front Mllb, front M2 back Mlm Front X00, front [00, front Mia The coil of relay T is locked in through front Tc.

The Major Counter United (FIG. 2F) includes major counters HA'-HS and major counters KA'-KS. Major counters PIN-HS and KAKS each include 50 contacts arranged in a circle. As the coil HA or KA is actuated the wiper of this major counter moves sequentially from contact 1 to contact 50. As H8 or KS is actuated the wiper moves in the opposite direction. The Major Counter Unit also includes the relays NS, NA, MS, MA and the relays HN and KL. HN and KL cooperate to prevent the wipers of the Major Counters from passing from the last tap or the next to the last tap (Hww or Hxx or Kww or Kxx) to the first tap (Ha or Ka) or from the first or second tap (Ha or Hb or Ka or Kb) to the last tap (I-Lrx or Kxx). The contacts of the major counter HA-HS are connected to potentiometer POTX. This potentiometer includes a plurality of resistors which are connected in series between conductors LP and LN. As the wiper of the major counter moves it changes the relative number of resistors connected between each of the conductors and the wiper and thus the potential derivable from POTX. The major counter KA-KS' is similar to the Counter HAHS' and is similarly related to potentiometer POTY. In addition to the taps connected to the resistors, the major counters include a plurality of taps HAin, HSin, KA'in, KSin. These contacts are normally closed and are opened and reclosed during each movement of the wiper from one of the counting contacts to the other.

The Minor Counter Unit (FIG. 2B) includes minor counters N-NR and L-LR. The Minor Counter Unit also includes the relays N1B, N4B, LIB, LIB, HA, HS, KA, and KS. Major counter HA'HS is controlled by minor counter N-NR and major counter KA-KS is controlled by minor counter L-LR. Counters N-NR and L-LR have a plurality of taps which may be of the order of eight, The Wipers of these counters move from one tap of the succeeding one as the actuating coil N or L of the counter is energized. The counters are reset by the reset coils NR or LR. The counters N and L include contacts Nz'n and Lin which are opened and reclosed during each movement of the wipers from one counting contact to the succeeding one.

The counting contacts of the Minor Counters N and L are labeled in the same manner as the other contacts, by lower case letters. But in this case, the contacts are labeled in sequence to correspond to the order in which they are engaged by the wiper. That is, the contact La is the first contact of L engaged by the wiper, the contact Ld is the fourth contact of L engaged by the wiper. The relays N and L also have off-normal contacts labeled No and L0. These contacts may be front or back and are closed or opened respectively when the Wiper moves from its zero position.

The coil N is adapted to be connected between conductors LP and LN through back HSa, back HAa, front NAa, or front NSa in parallel. The release coil NR is adapted to be connected between LP and LN through front N0, and either back Td or front RV and back NTa. The coil L and the release coil LR are analogouslv M nected.

The coils of LlB, NIB, L4B, N4B are adapted to be connected between conductors LP and LN through La, Na, La' and Na, respectively (that is the first taps and the fourth taps). The coils of HA, HS, KA, KS are adapted to be connected between conductors LP and LN through backs Ha'in, HS'in, KAin and KSilz, respectively. The coil HA is adapted to be connected between LP and LN through the following circuits:

Back N4Ba, back STZa, front M11 or M3 back X2a, back RV a, back TCb, front PXa, back HNc, front Ta, back Nin, back FCa.

Back N tBa, back STZa, front M212, back RVa, back TCb, front PXa, back HNc, front Ta, back Ni/z, back FCa. Back N4Ba, hack STZa, front Mlf or front M3), back X2a, front RVh, front NTg, front QXa, back HNc, front Ta,

back Nin, back FCa.

Back N4Ba, back ST2a, front M2b, front RVh, front N2g, front QXa, back HNc, front Ta, back Nin, back FCa.

Back NfBa, front STZg, back M4g, back RVa, back TCb, front PXa, back HNc, front Ta, back Nin, back FCa.

Back NlBa, front ST 2g, back M4g, front RVh, front NTg, front QXa, back HNc, front Ta, back Nin, back FCa.

The coil HS is analogously connected.

It appears desirable to discuss briefly the significance of these circuits. The counters HA-HS' are both actuable only in modulo 1, 2 and 3 both in state 1 and in state 2. In state 1, modulo 1 and 3 HA'-HS are only actuable with X in status 0 or 1, in modulo 2 with X in any status. In state 1 major counter HAHS is actuated through N4Ba in state 2 through NlBa. With RV and TC unactuated HA is actuable through PXa, that is, when the X increment is positive, and HS through QXb, that is, when the X increment is negative. The converse exists when RV is actuated and NT is also actuated. The significance in this is that when the major counter HAHS' is advanced with the increment positive, it is returned to the initial position after the polarity change by actuation of RV and NT if the X increment has been reversed following a failure. The converse occurs when the advance of Major Counter HA HS is advanced with a negative X increment.

With the modulo and the polarity set the operation of the major counter HAHS' is controlled by the relay through front Ta. Back Nin serves for counting and FCa disconnects the major counter during drift.

The repetition is produced by relay N through back Nin. The number of operations of the Counter is controlled by back N4Ba in state 1 and by back NlBa in state 2. Since N48 is actuated after four counts of N and N1B after one count of N, it is seen that in state 1 major counter HAHS advances four units for each actuation of T in state 1 and only one unit in state 2. Thus, the increments introduced in state 1 are four times as great as the increments in state 2.

Major counter KA'KS is connected analogously to major counter HA'HS, and the operation of the latter will be understood from the above comments.

Register B (FIB. 2C) includes relays 131 through B7, relay BS and relay B. The coils of relays B1 through B7 are connected to LN through back EBa. Thus when EB is actuated, Register B is reset. The actuation of the coils B1 through B7 is controlled by relay DB through front DB through DB1, respectively. The coils are adapted to be connected selectively to the conductor LP through DB through DB1, respectively, and through selected contacts Da through Dg which define the magnitude of the operation of the Controlled System as a binary number. The contacts Da to Dg may be the contacts of a Digi-Coder converter which converts a voltage derivable from the Controlled System into a binary number. Such a converter may be bought from Fischer 8: Porter Co. of Hatboro, Pa. Thus, with DB actuated, the actuation of relays B1 through B7 define the operation of the Controlled System as a binary number. The 

